Input Signals for HFM SFI/Ignition System
Input Signals for the HFM Sequential Mulitiport Fuel Injection/Ignition System
Input Signals:
Engine Speed, Crankshaft Position, Ignition Circuit Recognition
Information regarding engine speed, crankshaft position and ignition circuit recognition is transmitted from the crankshaft position sensor (L5) in the form of alternating voltage to the engine control module. A analog-to-digital converter transforms the alternating voltage signal into a square wave signal (TN-signal).
Engine speed is calculated by timing every half revolution of the crankshaft.
The crankshaft position is determined by voltage signals from the flex plate segment (A).
Recognition of ignition circuit 1 for cylinders 2 and 5 is transmitted by a permanent magnet on the segment (arrow).
The engine speed, crankshaft position and ignition circuit 1 recognition signals are required for the engine control module to perform the following functions:
- Fuel injection:
- minimum injected fuel quantity,
- start control,
- injector sequence synchronization,
- warm-up enrichment,
- acceleration enrichment,
- WOT (full load) enrichment,
- deceleration shut-off.
- Ignition:
- at start,
- during warm-up,
- at CTP (idle),
- at WOT (full load),
- at deceleration shut-off.
- Catalyst warm-up.
- Charcoal canister purging.
- Camshaft adjustment.
- Anti-knock control.
- Engine rpm limiter.
- Transmission overload protection.
Camshaft Position, Ignition TDC, Cylinder 1
The camshaft position sensor (L5/1) transmits an alternating voltage signal for every 20° rotation after TDC. This signal is converted into a square wave signal by the analog-to-digital converter and processed by the engine control module.
The camshaft position signal is required by the engine control module to perform the following functions:
- Fuel injection:
- injector sequence synchronization.
- Ignition:
- at start,
- fuel shut-off during ignition failure,
- anti-knock control.
Vehicle Speed Signal
The vehicle speed signal is transmitted from the ABS/ASR or ABS control module (N3O/1 or N30), to the electronic accelerator control module (N4/1) or the cruise control/idle speed control module (N4/3) and on to the engine control module (N3/4) via CAN.
The vehicle speed signal is required by the engine control module to perform the following functions:
- Fuel injection:
- deceleration shut-off.
- Engine rpm limiter.
- 2->3 upshift delay.
- Drive shaft - maximum rpm limitation.
Engine Coolant Temperature
The NTC engine coolant temperature sensor (B11/3) measures engine coolant temperature and converts the temperature reading to an electrical signal.
Negative Temperature Coefficient = (NTC)
The resistor, with semiconductor, decreases its electrical resistance with increasing temperature.
The engine coolant temperature signal is required by the engine control module to perform the following functions:
- Fuel injection:
- start control,
- after-start enrichment,
- warm-up enrichment,
- acceleration enrichment,
- deceleration shut-off.
- Ignition:
- at start,
- at warm-up,
- at CTP (idle),
- at deceleration shut-off.
- Catalyst warm-up.
- Charcoal canister purge.
- 2->3 upshift delay.
- Camshaft adjustment.
- Overheat protection.
- Camshaft adjustment.
- Anti-knock control.
Intake Air Temperature Sensor (B17):
Intake Air Temperature
The intake air temperature sensor (B17) reads the air temperature in the intake air flow and converts that value into electrical signals. These signals are processed in the engine control module and used to correct injection duration and ignition angle.
The intake air temperature sensor, like the engine coolant temperature sensor, consists of a NTC resistor.
The intake air temperature sensor signal is required by the engine control module to perform the following functions:
- Fuel injection:
- warm-up enrichment.
- Ignition:
- intake air temperature correction.
- Charcoal canister purge.
Closed Throttle Position Switch (M16/1):
Closed Throttle Position (Idle) Recognition
CTP (idle) is recognized by the Closed Throttle Position (CTP) switch (M16/1s2 or M16/2s2) in the electronic accelerator actuator (M16/1) or cruise control/idle speed control actuator (M16/2). The respective control module (N4/1 or N4/3) transmits this information to the engine control module (N3/4) via CAN.
The CTP signal is required by the engine control module to perform the following functions:
- Fuel injection:
- warm-up enrichment,
- deceleration shut-off.
- Ignition:
- at CTP (idle).
- Catalyst warm-up.
Throttle Valve Position
The throttle valve position is transmitted by the throttle valve actual value potentiometer (M16/1r1 or M16/2r1) in the electronic accelerator actuator (M16/1) or cruise control/idle speed control actuator (M16/2). The respective control module (N4/1 or N4/3) transmits this information to the engine control module (N3/4) via CAN.
The throttle valve position is required by the engine control module to perform the following functions:
- Fuel injection:
- minimum injection quantity,
- acceleration enrichment,
- WOT (full load) enrichment,
- deceleration shut-off.
- Ignition:
- at WOT (full load).
Heated Oxygen Sensor (G3/2):
Oxygen Sensor Signal
The heated oxygen sensor (G3/2) measures the residual oxygen content in the exhaust gas.
The heated oxygen sensor extends into the exhaust stream and sends the engine control module a voltage signal dependent upon oxygen content.
The voltage signal varies as follows:
Correct mixture: 450 mV,
Rich mixture: 500 - 1000 mV,
Lean mixture: 100 - 400 mV.
The oxygen sensor signal is required by the engine control module to perform the following function:
- Lambda control.
Knock Sensors (A16):
Knock Sensor Signals
The knock sensors (A16) consist of two piezoelectric solid noise sensors.
Engine block vibration is transmitted onto each piezo ceramic and is sent as an alternating voltage signal to the engine control module via a shielded cable.
NOTE: Piezo effect = voltage generated by pressure on a fixed ceramic.
Knock Sensors (A16):
The knock sensors (A16) are located on the engine block, beneath the intake manifold. This location point was chosen so combustion knock on all cylinders could be detected.
The knock sensor signals are required by the engine control module to perform the following function:
- Ignition:
- anti-knock control.
Transmission Range
The transmission range signal is transmitted from the electronic accelerator control module (N4/1) or the cruise control/idle speed control module (N4/3) to the engine control module via CAN.
The transmission range signal is required by the engine control module to perform the following functions:
- Fuel injection:
- after-start enrichment.
- Catalyst warm-up.
- 2->3 upshift delay.
- Camshaft adjustment.
- Engine rpm limitation.
Transmission Overload Protection Switch (S65):
Transmission Overload Recognition
The transmission overload protection switch (S65) is designed as a hydraulic pressure switch and is connected to the working pressure circuit of brake band B1. The actual switch function of the overload protection switch is dependent on B1 working pressure.
The opening and closing of the overload protection switch (S65) is recognized by the engine control module as a switch signal.
The switch signal is required by the engine control module to perform the following function:
- Transmission overload protection.
Battery Voltage and Voltage Supply
The injected fuel quantity is determined by injection duration. Injection duration is influenced by battery voltage. In order to equalize the injected fuel quantity under fluctuating battery voltage conditions, the engine control module corrects the injection duration.
Example:
Low battery voltage = longer injection duration,
High battery voltage = shorter injection duration.
Overvoltage Protection Relay Module:
Voltage for the engine control module (N3/4) is supplied directly from the overvoltage protection relay module (K1/2).